The Neuroscience of Trust

Researchers have pinpointed two brain regions associated with trust.

Have you ever been betrayed by someone that you trusted completely even though gut instincts gave you early warning signs that he or she might not be trustworthy? Recent neuroscientific research shows that in many ways our brains are hardwired to trust others. This aspect of our human nature is one reason that having your trust betrayed can short-circuit your neurobiology and make it difficult to trust again.

Recently, I was betrayed by someone that I trusted wholeheartedly and considered to be a best friend. Being double-crossed by someone I trusted caused every neural network and association of friendship or camaraderie with that person to dissolve on a neurobiological level.

Once I realized the extent of the malevolence, I could literally feel the neural networks and brain regions associated with trust disengage and shut down. Neural networks and brain regions that had formerly been associated with positive emotions and magnanimity towards this person were replaced with animosity, suspicion, and resentment.

Forgiveness towards the person who betrayed me remains a work in progress... Can you relate? Is there someone in your life that you're trying in vain to trust again?

One of the silver linings of having my trust broken was that it forced me to practice what I preach in terms of Loving-Kindness meditation (LKM), not holding a grudge, and equanimity. Unfortunately, writing about this experience still causes my stresshormones like cortisol to spike and my oxytocin levels to diminish. I can picture my ventral striatum deactivating as I revisit these intense feelings of mistrust.

Striatum in red.

Source: Wikimedia/Life Sciences Database

What Is the Neuroscience of Trust?

For the recent study, participants were under the illusion that they were playing an economic investment game with three different players: a close friend, a stranger, or a computerized slot machine. In reality, in every instance the participants were actually playing against a computer with a simple algorithm that systematically reciprocated actions worthy of trust exactly 50 percent of the time.

Based on perceptions of trust, the participants reported positive interactions with the "close friend" to be more rewarding than interactions with a stranger or slot machine—and were more likely to invest with this player. This illustrates our innate human desire to connect with others and create close-knit bonds even if these ties are based on blind trust or lead to Ponzi schemes.

Brain imaging of the participants showed that two specific brain regions were actively engaged when someone thought they were trusting a close friend. Increased activity of the ventral striatum and medial prefrontal cortex were correlated with positive social value signals when participants made decisions based on a belief they were playing with a good friend.

The ventral striatum is considered a key pathway in human reward processing and positive emotions. In a recent Psychology Today blog post, "The Neuroscience of Savoring Positive Emotions," I wrote about a study from University of Wisconsin-Madison that found a correlation between savoring positive emotions and sustained activation of the ventral striatum.

The medial prefrontal cortex is associated with how we perceive another person's mental state and monitoring what's happening outside our current focus of attention. The medial prefrontal cortex also plays a role in decision-making as well retrieving and consolidating memories.

Together, these brain regions provide additional evidence that participants felt a greater social reward when they believed their good friend had reciprocated cooperation during the game. Interestingly, feelings of trust occured despite the reality of the situation. Even though reciprocity occurred 50 percent of the time under every circumstance, participants consistently trusted the "good friend" more than the other imaginary players throughout the game.

Conclusion: Trust, Social Connectivity, and Well-Being Are Intertwined

This new study illustrates the mechanisms underlying the social value and importance of trust. The willingness to trust others is built into our DNA. Working together has always been key to the survival of our species. Having faith in one another is in the best interest of both the individual and the collective—especially in times of risk and uncertainty.

However, this experiment suggests that our instinct to trust can override logic. People can be fooled into trusting someone, even when the supposed "close friend" is actually no more loyal than a heartless computer algorithm. One reason that being betrayed by someone you trust is so jarring is the underlying vulnerability and gullibility of blind trust this experiment illustrates. Wanting to trust someone has powerful neurobiological roots, but genuine trust must be earned.

After being betrayed by a good friend, business associate or romantic partner, it can be difficult to give people the benefit of the doubt or blindly trust someone again. Maybe this is a good thing on some level? In a world full of scammers, having a healthy dose of pragmatic skepticism is probably a good idea. That said, collaboration and trust are essential for building healthy and strong interpersonal relationships. Ultimately, the social connectivity created by prosocial behavior and wholehearted, trusting relationships fortifies our well-being at the deepest level.

If you'd like to read more on this topic, check out my Psychology Today blog posts:

That was a great article on neurological underpinnings of trust. We need a lot more of those. I couldn't help but notice the sadness surrounding the piece about your experience of betrayal. I just wanted to let you know that I hope you're at a better place now.

The social mythology of trust is that it is assured reliance on another's behavior. But nothing about another's behavior is assured--nor can it be. Humans are simply not that consistent in their mode of action. Humans are not seat-belts or opiates or gravity. Trust is not able to guarantee anything at all except a negative outcome when betrayed.

Actual trust--the way it actually plays out in the world--is the expectation that positive past behavior will recur. This expectation when directed at humans is a delusion as the study you cite powerfully demonstrates. A fine example of the Framing Effect, in which how data is presented affects how it is interpreted, the study had all simulations behave identically by betraying the test subject half the time, yet the test subject considered one of the simulations to be more trustworthy due to experimental framing which triggered greater forgiveness for the infractions due to the mistaken perception of familiarity.

And that's really the mechanism here. Familiarity as assurance is a direct result of a common cognitive bias--it's an example of the Availability Heuristic which is the tendency to overestimate the likelihood of events with greater "availability" in memory, which can be influenced by how recent the memories are or how unusual or emotionally charged they may be. The familiar is the most available. No one is more familiar than a friend in the offered group for this experiment.

In this context, trust emerges from conspicuous recollections of rewarded expectation from an individual regardless of how often expectations were less than ideal or outcomes were actually negative but--and this is crucial--without reaching one's idiosyncratic sense of unacceptability. This study confirms that genuine lapses are ignored--Confirmation Bias--and that expectations of positively recurring behavior nonetheless remained high.

Trust is delusional. While it may be natural to some, to others it remains the fool's game it is.

Courage trumps trust. Accepting outcomes takes courage. Risking negative consequences takes courage. Trust requires not courage, but credulousness. If anything is hardwired into human DNA, then it is credulousness. Language, after all, did not evolve to discern truth, but to persuade. Most humans spend more time rationalizing, therefore, than being rational--a later evolutionary development that builds on rhetoric with logic--trust is a direct result of rationalization. Trust is a heuristic that pays off sufficiently often. But, instead of "working" (rationalizing with all your might) to trust again, instead of attempting to reboot the erroneous shortcut, consider being brave and accepting deception and betrayal and creating contingency plans for when your expectations are again dashed when next you play the odds (which is all that is ever done under the auspice of trust).